Compression-rheostat



. applications,

UNITED STATES PA'llazNT oFFIcE.

OTTO A. KNOPP, 0F OAKLAND, CALIFORNIA.

COMPRESSION-RHEOSTAT.

- To all whom t may concern.'

Be it known that I, OTTO A. KNoPP, a citizen of the United States, residing at the city of Oakland, county of Alameda, and State of California, have made a new and useful inventionto wit, Improvements in Compression-Rheostats and I hereby declare the following to be a full, clear, concise, and exact description of the same.

Among'the objects of this invention are to provide a rheostat having a wide range of great fineness of regulation, and large heat dissipating capacity.

In this specification and the annexed drawings, the invention is illustrated in the form considered vto be the best but it is to be understood that the invention is not limited to such form, because it may be embodied in other forms, andit is also to be understood that in and by the claims following the description, it is desired to cover the invention in whatever form it may be embodied.

So far as I amaware,-I am the first to surround or submerge a compression rheo-4 stat in oil or 'other nonLelectrolytic liquid. -Such submersion results' in greater uniformity in the action of the 'compression pile, higher efficiency, greater durability, more rapid dissipation of heat therefrom and superiorelectrical and mechanical advantages. The film of oil between each of the contacting conductors forming the pile, prevents arcing and sparking therebetween, insures the positive and uniform separation between each and all of the conductors under variations of mechanical pressure on-the pile;

' whereas a` pile of dry disks or conductors do not separate uniformly and are apt to stick together in groups and separate proportionately too far apart at other points, setting up arcing and sparking that breaks down the opposing surfacesv of the disks, destroying their usefulness and interfering with the uniform resistance of the pile as a whole, points with a resultant concentration of heat, whereas the resistanceshould be uniform throughout the pile. The oil isalso particularly valuable as a dssipating agent for conducting heat away from the pile. p In the accompanying one sheet of d-raw- 1n s:

igure 1 is a front elevation partly in cross section, illustrating a simple form of the invention arranged for manual .control of the compression of the rheostat pile.

Specification of Letters Patent. atented June 29, 1920, Application filed October 16, 1916. Serial No. 125.862. v

v ends forming a hermetically sealed chamber with the outer casing 1. The compression rheostat 5 is composed of disks of carbon, graphite, or other suitable material in superimposed arrangement as illustrated; the pile resting upon the lower plug 4. A piston composed of the circular headslj and 7 spaced apart by the rod 8, is interposed between the pile 5 and the plug 3. This piston is of electro-conductive material. 4 justing screw 9 is threaded in the plug 3 and has the insulating knob 10, by means of which the screw may be turned. The lower end of the screw 9 is pivoted in the piston 7, whereby the pressure on the resistance pile 5 may be regulated by advancing or retracting the screw 9. The coil spring 11 eX- panding between the head 7 and the annular ring-12 is provided to take up lost motion in ythe threaded engagement between the screw 9 and the plug 3, to permit a finer and more the top forced under compression by the cap 16 Ascrewed onto the casing 1.

The current passing through the pile passes into the device through the terminal 17, held in Contact with the plug 3 by the binding nut 18 threaded thereon; passes through the screw 9; through the piston; through the resistance pile 5, and passes out the terminal 19 fixed in the plug 4 by Athe binding screw 20.

Before screwing in the plug 3 and sealing the casing the latter is filled with oil or other suitable liquidto entirely submerge the p1le 5. Practice has proven that the film of liquid between the different disks forming the compression rheostat unit 5, does not to any practicable extent increase the resistance of this unit. It has been vfurther observed The ad- 1 of compression rheostat that may that the ineness of re lation of the rheostat has been materia ly improved by the introduction of the oil, as the liquid increases the adhesive ower of the disks and prevents the parting of the rheostat or pile at any one point when the pressure becomes low, which prevents arcing between the different disk units, which arcing on a dry compression rheostat usually destroys rapidly the good regulating qualities of t e rheostat.

The invention operates substantially as follows: The resistance to the current passing through the pile 5 varies with 'the pressure applied thereto. Resistance to the current passing through the instrument is regulated by screwing down or backingoi the knob 10; the resistance is less when the pile 5 is compressed so that all the disks make good contact with each other; inversely, the resistance increases as the pressure is released and the several disks forming the pile are separated by the film'o oil. The vcurrent passing through the pile 5 generates heat, which is transmitted through the oil 21 which dissipates it by natural radiation from the metallic shell 1, with which the oil makes contact through the openings 22 in the insulation 2. The interposition of the spring 1 1 insures a uniform application and release of pressure by taking up the lost 'motion in the screw thread of the screw 9.

Fig. 2 illustrates diagrammaticall a form e operated from a remote control by appl 'ng the pressure to the pile magnetically. he construction includes the oil ti ht inclosing casing 23, havin an iron cla solenoid 24 submerged therein, suitably wound as at 25 to create a magnetic field when the terminals 26-26 are connected in circuit. The compression rheostat 27 is similar in construction to the rheostat pipe 5 and is connected in circuit to the terminals 28-28. When the coil 25 is excited the magnetic field created Y sucks in the core 29, the rise of which ,com-

presses the interposed spring 30 and applies pressure to the compression pile 27. The stem 31 of the core has -a tapered base `32, which acts as a valve for closing the openin 33 of the inclosing casin 24 of the solenoid. When the core 29 rises it displaces the oil confined in the space 34 which escapes through the gradually restricted opening 33 giving a dash pct effect compellin a graduated uplifting of the core 29 an the consequently graduated application of pressure to the pile 27, the oil contained within the;

se o

' I claim and desire to secure by Letters Patent' is:

1. A rheostat including an inclosing casing containin a liquid; a compression rheostat immerse in said liquid; a solenoid immersed in said liquid and havin a core adapted to com ress said compression rheostat; and a dasii pot between said core and the top of said solenoid.4

2. A rheostat including an inclosing casing containin a liquid; a compression rheostat immerse in said liquid; a solenoid having an opening with a restricted outlet; a core -in said o nin having a -tapered extension throng sai restricted opening and bearing against said rheostat.

3. A rheostat including an inclosing casing containin a liquid; a compression rheostat immerse in said liquid; a solenoid immersed in said liquid and havin a core adapted to compress said compression rheostat.

4. A rheostat including an inclosing casing containin a liquid; a compression rheo- 'stat immerse in said liquid; a solenoid imtiguous to said plunger forv regulating the tension on the rheostat disks.

In testimon whereof I have hereunto set my han'd at an Francisco, California, this 26th day of September 1916.

oir'ro A. KNoPP. In presence of- BALDWIN VALE, A. J. HENRY. 

